Download Molecules of Life

Chapter 5
Organic Compounds
Hydrogen and other elements
covalently bonded to carbon
Examples important to life are:
 Carbohydrates
 Lipids
 Proteins
 Nucleic Acids
Carbon’s Bonding Behavior
 Outer shell of carbon
has 4 electrons; can
hold 8
 Each carbon atom can
form covalent bonds
with up to four atoms
 It can bonds with itself
or other atoms
Ex. H-C=C-H
Bonding Arrangements
 Carbon atoms can form
chains or rings
 Other atoms project from
the carbon backbone
How do organic molecules react?
With their Functional Groups
 Atoms or clusters of atoms that are covalently bonded
to carbon backbone
 Give organic compounds their different properties
Examples of Functional Groups
Hydroxyl group
- OH in carbs and proteins
Amino group
- NH3+ proteins (basic)
Carboxyl group
- COOH fats and proteins
(acid)
Phosphate group
- PO3- nucleic acids (acidic)
Sulfhydryl group
- SH Between proteins
Types of Reactions
 Functional group transfer
 Electron transfer
 Rearrangement – one type of organic compound
changed to another Ex. Carbs to fats
 Condensation/dehydration synthesis
 Cleavage - splits
Condensation
Condensation Reactions
 Form polymers from subunits
 Enzymes remove -OH from one molecule, H from
another, form bond between two molecules
 Discarded atoms can join to form water
Hydrolysis
Hydrolysis
 A type of cleavage reaction
 Breaks polymers into smaller units
 Enzymes split molecules into two or more parts
 An -OH group and an H atom derived from water are
attached at exposed sites
Carbohydrates
Monomers - Monosaccharides
(simple sugars)
Dimers - Oligosaccharides
(short-chain carbohydrates)
Polymers - Polysaccharides
(complex carbohydrates)
Monomers = Monosaccharides
 Simplest carbohydrates
 Most are sweet tasting, water soluble
 Most have 5- or 6-carbon backbone
Glucose (6 C)
Fructose (6 C)
Ribose (5 C)
Deoxyribose (5 C)
 Functional group ____
Two Monosaccharides
glucose
fructose
Disaccharides
 Type of oligosaccharide
glucose
fructose
 Two monosaccharides
covalently bonded
 Formed by condensation
reaction
+ H2O
sucrose
Polymers = Polysaccharides
 Straight or branched chains of many sugar monomers
 Most common are composed entirely of glucose
 Cellulose
 Starch (such as amylose)
 Glycogen
Cellulose and Starch
Glycogen
 Sugar storage form in animals
 Large stores in muscle and liver cells
 When blood sugar decreases, liver cells
degrade glycogen, release glucose
Chitin
 Polysaccharide
 Nitrogen-containing groups attached to glucose
monomers
 Structural material for hard parts of invertebrates, cell
walls of many fungi
Lipids
 Most include fatty acids
 Fats
 Phospholipids
 Waxes
 Sterols and their derivatives have no fatty acids
 Tend to be insoluble in water
 Monomers are fatty acids and glycerol
Fats
 Fatty acid(s)
attached to glycerol
 Triglycerides are
most common
Fatty Acids
 Carboxyl group (-COOH) at one end
 Carbon backbone (up to 36 C atoms)
 Saturated - Single bonds between carbons
 Unsaturated - One or more double bonds
Three Fatty Acids
stearic acid
oleic acid
linolenic acid
Phospholipids
 Main components of cell membranes
Waxes
 Long-chain fatty acids linked to long
chain alcohols or carbon rings
 Firm consistency, repel water
 Important in water-proofing
Sterols and Derivatives
 No fatty acids
 Rigid backbone of four
fused-together carbon
rings
 Cholesterol - most
common type in animals
Amino Acid Structure
carboxyl
group
amino
group
R group
Properties of Amino Acids
 Determined by the “R group”
 Amino acids may be:
 Non-polar
 Uncharged, polar
 Positively charged, polar
 Negatively charged, polar
Protein Synthesis
 Protein is a chain of amino acids linked by peptide
bonds
 Peptide bond
 Type of covalent bond
 Links amino group of one amino acid with carboxyl
group of next
 Forms through condensation reaction
Primary Structure
 Sequence of amino acids
 Unique for each protein
 Two linked amino acids = dipeptide
 Three or more = polypeptide
 Backbone of polypeptide has N atoms:
-N-C-C-N-C-C-N-C-C-None
peptide
group
Protein Shapes
 Fibrous proteins
 Polypeptide chains arranged as strands or sheets
 Globular proteins
 Polypeptide chains folded into compact, rounded shapes
Primary Structure & Protein Shape
 Primary structure influences shape in two main
ways:
 Allows hydrogen bonds to form between different
amino acids along length of chain
 Puts R groups in positions that allow them to
interact
Secondary Structure
 Hydrogen bonds form between different parts of
polypeptide chain
 These bonds give rise to coiled or extended pattern
 Helix or pleated sheet
Examples of Secondary Structure
Tertiary Structure
heme group
Folding as a result
of interactions
between R groups
coiled and twisted polypeptide
chain of one globin molecule
Quaternary Structure
Some proteins are
made up of more
than one polypeptide
chain
Hemoglobin
Enzyme Structure
and Function
• Enzymes are catalytic molecules
• They speed the rate at which reactions
approach equilibrium
Four Features of Enzymes
1) Enzymes do not make anything happen that could
not happen on its own. They just make it happen
much faster.
2) Reactions do not alter or use up enzyme molecules.
Four Features of Enzymes
3)
The same enzyme usually works for both the
forward and reverse reactions.
4) Each type of enzyme recognizes and binds
to only certain substrates.
Activation Energy
 For a reaction to occur,
an energy barrier must
be surmounted
activation energy
without enzyme
starting
substance
 Enzymes make the
activation energy
with enzyme
energy barrier smaller
energy
released
by the
reaction
products
Factors Influencing
Enzyme Activity
Temperature
pH
Salt concentration
Allosteric regulators
Coenzymes and cofactors
Polypeptides with Attached
Organic Compounds
 Lipoproteins
 Proteins combined with cholesterol, triglycerides,
phospholipids
 Glycoproteins
 Proteins combined with oligosaccharides
Denaturation
 Disruption of three-dimensional shape
 Breakage of weak bonds
 Causes of denaturation:
 pH
 Temperature
 Destroying protein shape disrupts function
Nucleotide Structure
 Sugar
 Ribose or deoxyribose
 At least one phosphate group
 Base
 Nitrogen-containing
 Single or double ring structure
Nucleotide Functions
 Energy carriers
 Coenzymes
 Chemical messengers
 Building blocks for nucleic acids
ATP - A Nucleotide
base
three phosphate groups
sugar
Nucleic Acids
Cytosine
 Composed of nucleotides
 Single- or double-stranded
 Sugar-phosphate backbone
Adenine
DNA
 Double-stranded
 Consists of four types of
nucleotides
 A bound to T
 C bound to G
RNA
 Usually single strands
 Four types of nucleotides
 Unlike DNA, contains the base uracil in place of
thymine
 Three types are key players in protein synthesis